Method and apparatus for the production of music



June 27, 1933. B. F. MIESSNER ET AL 1,915,350

METHOD AND APPARATUS FOR THE PRODUCTION OF MUSIC Original Filed May 20, 1931 4 Sheets-She et 1 IN V EN TORS:

June 27, 1933- B. F. MIE SSNER El AL METHOD AND APPARATUS FOR THE PRODUCTION OF MUSIC Original Filed May 2o,' 1931 4 Sheets-Sheet 2 I INVENTOkS-" June 27, 1933. B. F. MIES'SNER El AL 1,915,350

METHOD AND APPARATUS FOR THE PRODUCTION OF MUSIC Original Filed May 20, 1931 4 Sheets-Sheet 4 IN V EN T 0R5:

UNITED STATES PA-TENT oF IcE p BENJAMIN I. MIESSNEB, OF KILLBUBN TOWNSHIP, ESSEX COUNTY, CHARLES T. JACOBS, OF NEW PROVIDENCE TOWNSHIE UNION COUNTY, NEW JERSEY, ASSIGNORS TO MIESSNER INVENTIONS, INC., A CORPORATION OF NEW JERSEY METHOD AND APPARATUS FOR THE PRODUCTION OF ZEUSIO Application filed Kay 20, 1931, Serial No. 538,773. Renewed May 21,- 1932.

i This invention relates to musical nstruments and systems wherein the vibrations of tuned bodies are translated into electric oscillations and such oscillations employed for the actuation of further apparatus; and more particularly to the control of the amplitude time characteristics of the musical tones I thereby produced. The invention, although useful with any form of tuned body and with any mode of excitation thereof, is illustrated in connection with strings causedto vibrate by percussion. Instruments of the class described and improvements therein have been disclosed generally in the co-pending application of Benjamin F. Miessner, Serial-Number 512,399, filed January 30, 1931; and cer-.

tain improvements more specifically relating to the translating devices therein have been disclosed in theco-pending application of Benjamin-F. Miessner, Serial Number 528,- 750, filed April. 9, 1931.

The herein described invention is concerned primarily with the control, adjustment and variation of the initial and early amplitude-time characteristics of the musical tones electrically produced by such instruments, including the reduction or elimination of initial high amplitude; and also with the rate of damping of the tones upon release .of the key in a key-operated musical instru-' vment of the class describedz- Thus, for example, by the employment of the present invention in one of it's-forms the tones of an instrument otherwise generally piano-like in their amplitude-time characteristics may be marked advantage over the lattenof the constripped when desired of their percussionproduced attribute of'high initial amplitude.

and thereby rendered organ-like. A key-operated, piano type of electrical musical instrument,thus made-when desired or at all times. to simulate an organ, possesses the trol of the g'eneral'amplitude of individual tones resulting from the many ossible different manners of depressiono the several keys, or the touch as it is musically termed,

which is of course of no significance in the playing of a conventional organ. Our invention furthermore may make available tremolo efiects of individual tones, an availability not present in the usual organ.

Thus it is an object of our invention to provide, in a musical instrument or system of.

the class described, methods and apparatus for reducing or eliminating a high initial 0ut 7 put tone amplitude; and it is a further and allied object to provide methods and apparatus for delaying until appreciably after commencement of a tone theinstant of maximum amplitude thereof; and a still further and allied ob ect is the provision of methods and apparatus for delaying after key depression a the commencement of the tones produced by a key-operated instrument of the class described. Another object is the provision of methods and apparatus for controlling the rate. of damping u on key release of the tones produced by a ey-operated instrument of the class described; and still another object is the provision of means and methods for another instrument or selectively the tones of a plurality of other instruments; and it is a specific object to provide an electrical, keyoperated musical instrument possessing simultaneously all or any of the following characteristics; selective availability of different tone qualities, selectiveavailabi'lity of difierent amplitude -time characteristics,

ability to produce tremolo effects of individualtones, and-responsiveness to manner of key depression, or -touch. Other and allied objects will more fully appear from the following specification and the appended claims. v

The general principle involved in our inventionisthat of varyingthe efiiciency of translation into electric oscillations of the vi-. brations of the several tuned bodies, such variation being coincidentally produced with the manipulation of the key or other control of the vibration, insuch a manner as for example to provide low or zeroefliciency at I latte 5 tones is capable of modification and enlargement, and of bein carried out b a variety of combinations 0 apparatus, as 'ereinafter more fully appears.

In the detailed description of our invention, hereinafter set forth, reference is had to the accompanying drawings, of which Figure 1 is a view, partly plan and partly schematic, 'of a portion of a musical instrument embodying our invention in one form; Figure 2 is a vertical cross-sectional view, taken along line 22 in Figure 1, in which certain further mechanical details appear; Figure 3 is a view, similar to Figure 1, illustrating a modification of our invention; Figure 4 is a vertical cross-sectional view, similar to Figure 2, illustrating 'a detail'of the modification shown in Figure 3; i

Figure 5 is a view, similar to Figures 1 and 3, illustrating a further modification of our invention; and

Figure '6 is' a group of four oscillation curves illustrating the action of our invention in certain of its forms. y

In Figure 1 we show, partly schematically, a musical instrument embodying our invent1on in one form. In this figure will be seen a plurality ofstrings 1, strun' between tunmg pins 2 in insulating front pink 3 and pins f1 1n insulating rear member 5, over insulatmg triangular bars 6 to limit the active vibratory portion thereof. A hammer 7 may be provided under by' a key 8 through the medium of a repeating action 9, shown in Figure 2, a vertical cross-sectional yiew taken along the line AA in Figure 1; such an action is well known as acomponent of the grand piano. A damper 10, also actuated by key 8, may be provided for eachstring if .desired. The keys maybe pivoted as, at 58 and held in lateral alignment at the front by guidepins "-57, as willbe understood.

Washers about lateral guide pins 57, customarily employed/for limiting the downward motion of -"the" "front of keys .8, are omitted; and their function is performed b com onents 56, 55, 15, 16 and 17. Thus-1 may a pile of thin, circular, hi 'h =resi stance graphite or similar discs, each p e on a common electrically conductive plate 20; 16 may be an electrically conductivebutton or plunger aflixed to the bottom of an electrically conductive spring 15 and by the latter held with light pressure against top of pile 17 may be a felt button aflixed "tothetop of sprin 15; and 56 may be an adjustin screw in t e bottom of key 8, hexheaded inexaxnple. Piles 17 ma rest on 55 late 20 in holes 18 in front bar 19' w ich ma of non-conductive arid whic l each string to vibrate the Each hammer 7 may be actuatedmin'g the may be mounted springs 15. Depression of the front'end of key 8 will thus be seen to bel liiiited bythe resulting compression of 1 e p In order to translate the vibrations of the strin s 1 into electric oscillations, acapacity may formed between each-strin and a bar 11 and a bar 12, such bars'being msulatedly mounted underneath the strings an insulating blocks 13. Each of these bars may be connected to the grid of a thermionic vacuum tube, such tubes being shown as 21 and 22 respectively in Figure 1. The cathodes of these tubes may beenergized by battery or other current source 53; and their grids may be biased negatively with respect to their cathodes, through resistors 31 and 32 rerespectively, b the flow of their anode current through condensively byassed -resistor 23, as Wlll be understood. n the output. circuits of these tubes may be provided transformers'24 and 25, respectively; and a common battery or other anode current source 26 may be employed for the two tubes.

Across the secondary of transformer 24 may be provided otentiometer 27 and across the secondary 0 transformer 25 center tapped potentiometer 28. Avariable portion of each of these two potentiometers'may form a series circuit with the entire resistance of 'potentiometer '29 as shown; and between the variable contact and one end of the resistance of potentiometer 29 may be connected the input of an electrical amplifier 33, to the outputof which may' be connected loudspeaker or other electro-acoustic translating device 34. Electrostatic shielding 61 may advantageously be provided about the tubes' 21 and 22 and their associated apparatus, about the leadsto their grids, and'partially about the strings 1, bars 11- and l2, etc.

In order to make the capacities'formed betweenthe several strings 1 and the bars 11 and 12 effective in translating the string vibrations into electric oscillations, a potential difference must be established between the strings and such bars. This is accomplished for any string whose associated key 8 is depressed by an electrical circuit includin the pile 17, plunger 16 and spring 15 associated with the particular key. Such. a pile, plunger and spring will recognized by those skilled in the art as constituting a resistance whose value variesaccording to the pressure exerted on pile 17 by plunger 16 and will hereinafter b'e-referred to as variable resistance 14: it will thus be understood that a there isassociated with each key a resistance,

normally high, which is reduced to a relatively low value by the last portion of the depression of the key. Each string 1 may be sister. 41; and. each variable resistance 14 wired i its associated spring 1 5i e., to one sideof its asses. ciated variable-resistance =14through a remaybe by-passed by a condenser 40 connected between such spring and the commonside of all the variable resistances. This common side may be connected to a point of different potential than bars 11 and 12; and this point may conveniently be a point of positive potentialin battery or source 26 or a point rendered still more positive; by an additional battery or source such as 47. Each string is further connected, through a capacity 42 and a resistor 43 in parallel, either to a point of the same mean D. C. otential as that of the bars 11 and 12 or prje erably to a point of slightly more negative potential, as to the movable contact of a potentiometer 44 shunting a battery or source 45 in series with the negative terminal of 26.

Consideration being given to the manner of functioning of the apparatus shown, it will be seen that, unless the variable resistance 14 be infinite when key 8 is in itsnormal or raised position, current will flow from the.

positive terminal of battery or source 47 through each pile 17, associated plunger 16 and spring 15, and associated resistors 41 and 43 to the negative terminal of battery or source 26 or. as shown, to a point of more negative, adjustable potential-i. e., the-- slider of potentiometer 44. Withall keys in their normal position it is desirable so to adjust this potential that the voltage drop across each resistor 43 approximately equals that across the upper-shown half of potentiometer 44, thus rendering the potential of the several strings 1 at leastlapprox'imately the same asthat of the negative terminal of battery 26 and hence as that of the bars 11 and 12. The degree of this approximationdepends onthe accuracy of this adjustment and on the uniformity each between themselves of the normal resistances of the several variable resistances ,14, of the values of the several resistors41,and of the values of the several resistors 43., Under these circumstances, therefore, were the strin to vibrate, little or no translationof its vi ration into electric oscillations would take place.

Upon depression of any key 8, not only is the associated damper 10 lifted from and hammer '7 caused to strike string 1, butv the resistance of the associated variable resistance 14 is reduced, tending to raise the mean D. C. potential of string 1 and thus to make the capacities between string 1 and bars 11 and 12 effective in translating string vibra-' tion into oscillations, as will be understood. Due to the time required for condenser 40 to reduce its charge and for condenser42 to in-" crease its charge,however, the potential of string 1 cannot change in the practically instantaneous manner in which the resistance 14 is changed. The translation efliciency therefore rises slowly from its low or zero value to its new value. B suitable choice of the values of the several components the rate ofrise of translation efliciency may be nicely adjusted. Upon release of key 8 and consequent raising of the value of resistance .14, the original conditions are restored, also gradually rather than abruptly, at a rate also determined by the values of the components. I

The vibration-produced variation of the capacity between string 1 and each of the bars 11 and 12 will cause such potential as exists between the string and each of the bars to vary; andthus there is produced across each of resistors 31 and 32 anA; G. voltage substantially corresponding in its characteristics, including harmonic structure, to the vibration of the mean string point opposite the respective bar. This action'is similar to that of the well-known condenser microphone; and the amplitude of the voltages across resistors 31 and 32 at any instant will be seen to be a function of the mean potenj tial'diflerence between the string and the bars. Thus to such extent as this potential is delayed in rising to full value, the efliciency of translation of the string vibration into electric oscillations is delayed in its rise from zero to normal value.

The A. C. voltages appearing across resistors 31 and 32 are amplified respectively by tubes 21 and 22 and transformers 24 and 25, and appear across respective potentiometers 27 and 28. From these potentiometers such voltages, each regulable in amplitude and that across center-tapped potentiometer 28 regulable in phase with respect to that across potentiometer 27, may be applied to potentiometer 29; and from this potentiometer a composite voltage of regulab le amplitude may be applied to and amplified by electrical amplifier 33, the output of which is translated into sound by loudspeaker 34;

One of the bars 11 and 12, one of the tubes I the vibrations of the mean string points opposite the two bars 11 and 12, the consequent difference in harmonic composition of 4 the voltages across resistors 31' and 32, and the infinite variety, of amplitude relationships and the dual' phaserelationships in which I these voltages may: be combined or alge-i br'aically added, after amplification, by variousadjustments of the potentiometers 27 and 28. The numberv of such separate translating systems need not of course-be limited to 'two, such number being only illustrative herein.--

Reference again being had to the electrical system associated with each separate key and string, it will be seen that this system comprises a variable resistance 14 shunted by a capacity 40, a fixed resistor 41, and a capacity 6, 42 andresistor 43 in parallel.

The variable resistance 14 and shunting capacity may be replaced desired by a simple key-operated make-and-break switch, the desired delay action still being produced by the time 10 required to charge condenser? 42 throughretem'; and that these modifications will notconstitute departures from the spirit or scope of our mvention, which in this form em-.

sistor 41. We have found, however, that the opening and closing of a simple switch almost invariably produces ob'ectionable clicks in the output of loudspea er- 34 and 1!} therefore prefer to employ a gradually-acting switch, such as 14 may be considered. .Even in this case some undesirable noise may e experienced upon depression and/or rise of the key and we therefore prefer to include the shunting condensers 40, which we have found helpful in eliminating such noise. If

the switch consists, as shown, of a variable resistance, and if this resistance has an appreciable-minimum value, resistor 41 may be omitted. Again, a fixed resistor may be substituted for the switch or variable resistance, and resistor 43 replaced by a key-operated switch or variable resistance, of normally zero or' low resistance and of high or infinite resistance upon key depression; .or a poten-.

, tiometerin-ay'be substituted for each resistor braces broadly the use of electrical reactance and resistance to produce a time lag in a change of translating efliciency caused by key depression.

. In general when all the elements shown are present, we prefer to employ resistances .very roughly of .the same order of value for 4} and 43 and a variable resistance 14 whose resistance "is varied by key depression from many times such v lueto a fra'ction thereof. We have found. i desirable to employ as small a capacity across the variable resistance 14 as is effective in eliminating or minimizing noise production thereby; and to adjust the rate of change of translation efiiciency principally by choice of value of capacity of condenser Thus, assuming other parameters to be fixed and condenser 40 .to'have -rl figligible delaying effect, if condenser 42 be. ofr ela'tively low capacity the rise of trans lation efliciency uponfkey depression will be rapid and little difierence will be produced I from the ordinary case in whichtranslation efliciency is maintained at all times; if the capacity of condenser 42 be of somewhat larga given capacity of condenser 42, by change of other 'elementsi. e., by increase of capacity 40, of the valueof resistor 41, etc.- and further that appreciable differentiation between rising and falling rates, upon key depress on and release respectively, may be made by adjustment of the relative yalues of resistors-41 and 43. Variation of the relative values of the resistors'and tlie minimum yalue of the variable resistance 14 will affect the potential across the strihg-bar capacities under conditons .of key' depression and hence will affect the'maximum" available translation efliciency; this may of course be compensated if desired by change of the total voltage applied acrossthe resistors by.'sources 47, 26 and 45. In any particular case and I for the production of any particular effect both the relative and ithe absolutevalues of the components may readily be determined by test, with the aid of the principles above enunciated.

In F igure-1 we also show a double pole, double throw switch 58, the poles of Wl'llCh have been assumed in the right-hand position, as shown, in the foregoing description. If, however, the poles of switch 58 be thrown to the left hand positionythe system fissoclated of the potential of point ;59. .Thus by the inclusion of switch 58 we provide an instrument, the early amplitude-time characteristics of whose tones may bealtered at will- .The delay action inthe instrument shown in Figures 1 and 2 is produced by rendering translation efliciencynormally small or abwith each key which includes the variable resent and in causing it -to' increase upon key ing figures, but modified therefrom in this respect. Thus the strings 1 'and their sup- 1 ports, etc hammers 7, keys 8, action 9, dampas in Figures 1 and 2; also the bars 11 and 12,,

. the several strings ers 10, guide pins 57, etc., may be provided vacuum tubes 21 and 22, and their immediately associated circuits, transformers 24 and 25, potentiometers 27, 28, 29 and 44, batteries or sources 47, 26 and 45,'amplifie'r 33, loudspeaker 34, switch 58 and shielding 61. Switches or variable resistances 14' may be provided, being from the component 14 in Figures 1 and 2 only in the inclusion of springs 62 and in the use ofan adjusting screw 56' which maybe provided with a protrusion to hold spring 62 in place.

In Figure 3, however, each string 1 is wiredto the spring 15 of its associated switch or ,Vathrough a resistor 71 shunted by a condenser 72; and each string riable resistance 14' may be provided with a capacity 73 to the common side, of the ,variable resistances 14. This-common side may be connected to the movable contact of potentiometer 44. Each string may also be connected through aresistor 74 to the positive terminal of battery or-source 47 or other point of. substantially diflerent potential from that of bars 11 arid flhe general manner of functioning of the apparatus shown in Figures 3 and 4 is simllar to that disclosed above for Figures 1 2, the outstanding that of the individual circuits associated with 1. It will be seen that unless the valueof the variable resistance 1.4 be infinite when key 8 is in itsnormal or raised position, positivei terminal of battery or source 47 Y hreach of the resistors 74 and through the associated resistor 71 and the associated variable resistance 14'. If the resistors71 be of a larger order of value than, resistors 74, audit the maximum value of the variable resistances 14' isof a still larger order, as we 'prefer to arrange these values, the con-' densers 73 will be charged to almost the full potential'of the string to-bar potentials will be seen to be equal to the potentials across condensers 73 less the potential across the upper-shown por-' tion of potentiometer 44, and translation efficiency is therefore being. maintained. At the same time a relatively low potential appears across condensers 72.

Upon depression of any key 8,

not only is the'associated damper 10 lifted from and hammer 7 caused to strike. string seen in Figure 4 to differ,

key

and P exception being, of course, p ace that the-eff ciency will have been rencurrent will flow from the.

sources 47, 26 and 45. The.

however,-

1, value of the associated variable resistance 14 is reduced, preferably to a value neghg1ble m comparlson to resisto' 74 and. 71. Thus condenser 72 is efiectiv paralleled v with condenser 73; and if the capacity of we prefer to make it, a large percentage of the charge normally present in condenser drop almost to t of condensers 72 and 73. Upon release of 7' the .value of 1 8 and; consequent raising of 72 be many times that of 73, as

73 will pass out therefrom into condenser 72,- causing the voltage across condenser 73 to e relatively low voltage originally present across condenser 72. Current will immediately begin to flow through resistor 74 into condensers 72 and 7 3, and will variable resistance 14', the ori 'nal conditlons are restored, the high vo tage across voltage by. discharge of the condenser through resistor 71. V In the case of Figures land 2, it is de- .condenser 72 being reduced to the original sirable that the switch or variable resistance,

14 be closed or reduced in value as late 1n the key stroke as' possible. The converse is true in the'case of Figures13and 4: hence the provision of spring 62. By virtue of this spring the first downward motion of key 8 is caused to exert pressure on pile 17; 1

spring 62 at or near the end of the stroke, and after compression of pile 17, compressing sufiiciently for the protrusion on screw 56 to bottom on felt button 55. Thus the drop of translation efliciency caused by deression of key 8 may be caused so to take dered low at the time'of the impact of hammerl7- with string 1. Residual eificiency atthis instant due to the residual voltage across condenser 7 3, may be minimized or eliminated by adjusting the slider of potentiometer 44 so that the voltage across its uppershown portion approximately equals such residual voltage, rendering small or zero the potential at this instant between string 1 and bars 11 and 12. v V

As in Figure 1, we show in Figure 3 a switch 58 for removing potential differences from the individual circuits associated with.

the several strings and comp7rising resistors 74 and 71, condensers 73 and 2, and vanable resistances 14' and for establishing these circuits and all their components, including at a fixed potential with respect to V strings 1,

bars 11 and 12. It will be understood, of 7 course, that the circuits and a paratus shown in Figure 3 are capable of mo ification within wide limits by those skilled in-theart, without departure from the novel method of render'-' ing translation efliciency momentarily low Q! a sent at the time of inception of vibration,-or of impact of hammer with string.

raised by key depression as in Figures land 2, but in which modified circuits are emloyed. The instrument may be largely simllar to that of preceding figures. Thus the strings 1 and their supports, etc., hammers 7, keys 8, action 9, dampers 10, guide pins 57 etc. may be provided as in Figuresl and 2; alsothe bars 11 and 12, vacuum tubes 21 and 22 and their immediately associated circuits, transformers 24 and 25, potentiometers 27, 28 and 29, battery 26; amplifier 33, loudspeaker 34 and shielding 61*. Switches or variable resistances 14" may be provided; of signilar form to those of Figure 1, but having piles 17 of much lower resistance, suitable for the control, from extremely low to normal value, of the filament current of two-element vacuum tubes 81, of which one is provided for each string.

In Figure 5 each string'is seen to be wired to the plate of its associated tube 81. The filament of each of these tubesis maintained in a practically extinguished, substantially non-emitting condition by the normal or maximum resistance value of the variable resistance or switch 14 connected to one side thereof, the common side of the variable resistances or switches 14" being connected through filament battery or. current source 82 to the other side of each of the filaments. One side of each of the filaments is also connected to the pole 83 of double-pole tap switch 85, whereby it may :be connected through a selectable inductance to a point of lower.

D. C. potential than that of bars 11 and 12. Such selectable inductance may be provided by a plurality of choke coils '86 or by a single,

tapped, high inductance choke coil; and such point of low D. G. potential may be the ne at1ve terminal of a battery or source 8%.

Each string 1 may also be connected to pole 84 of switch 85 through a resistor 88 and a condenser 89 in parallel. Switch 85, inits several positions excepting the up-most one as shown, will apply the potential of battery or source 87 across the individual circuits comprising tubes 81, strings 1, resistors 88 and condensers 89, through an inductance whose value depends on the setting of theswitch; in its upmost position it applies no potential to such circuits, but establishes them ata uniform negative potential'with respect to bars 11 and 12.

Again the general manner of functioning of the apparatus is as heretofore;"described, with the exception of the delaying circuits. With any key in itsnormal or raised position the plate-to-filament resistance of its associatedtube 81 is infinite or practically infinite, so that substantially no current flows therethrough from battery or source 87 and no voltage drop occurs in resistor 88. Thus string 1 is at the same D. C. potential as bars 11 and 12 and translation 'efiiciency is absent. Upon depression of any ke 8, however, not only is the associated damper 10 lifted from and hammer 7 causedto strike/ string 1, but the resistance value of the as sociated switch or variable resistance 14" mon circuit by the pole 83 of switch 85. The l voltage produced by the flow of this current through resistor 88 appears between'string 1 and bars 11 and 12, making the capacities I therebetween effective in translating string.

vibration into electric oscillations.

It will be appreciated that three factors other than switch or variable resistance 14" operate to delay the rise of potential between string 1 and the bars: the time required for the filament of tube 81 to reach normal emit-- ting condition after completion of its 'filament circuit, the time requlred to charge condenser 89, and the time required for the current through the inductance to change.

These factors need not all be simultaneously present: thus condensers 89 may be omitted;

orthey may be employed, for the purpose of rendering strings 1 at a low effective A. C. potential, of a small value producing negligible delaying effect. Again the inductance 86 may be omittedyor it may be employed in a single instead of a variable value.

The filament material and design of tube- 81 may be variously chosen to produce negligible or large delay in reaching emitting condition after completion of the filament circuit, as may be desired. If material of high thermal inertia be employed, 1t Wlll be seen that not only the attainment to full .value of translating efiiciency, but also the inception of the rise thereof from the normal ite period after excitation of the string 1.

With any of the arrangements hereinabove set forth, tremolo efl'ects on any 1nd1v1dual tone may be secured by the performer by a tion'efi iciency with change of key position which results from the values of the various components employed in a particular case. When translation efficiency is normally maintained at'a negligible or zero value and is raised only upon key depression, as is possible with the arrangements of'Figures 1 and 5, the mechanical dampers 10-may, if

desired, be omitted or permanently raised from the strings; cessation of the tones prolow or zero value, may be delayed for a definduced by string vibration then being affected entirely by the drop to zero value of translation efliciency upon key release. As above indicated, the rate of'drop, of efliciency in the case of Figure 1 is determined largely by the relation of condenser 42 to resistor 43; and the rate of drop in the case of Figure 5 is determined by the characteristic of tone characteristics the drop of emission of tube 81 upon extinguishment of its filament, the inductance employed as 86 and the relation of con denser 89, if employed, to resistor 88. Thus by control of the relations of the components, not only may initial amplitude-time be controlled, but also the terminal of such characteristics.

' vibrator excitation. Curve M may represent 1-: out

' low or, as shown, zero value at or just We include as Figure 6- of the drawings four illustrative oscillation curves, plotted against a horizontal time axis. In each case .-the point 0 denoteshorizontally the instant of excitation of a vibrator and vertically a zero value; the dotted line denotes the trans lation efiiciency with reference to the instant of excitation, and the heavy curve the instantaneous electric voltages produced by translation of the vibration ensuing such excitation. Thus curve K may represent a normal case wherein translation efliciency is maintained at all times. Curve L may represent oscillations produced in the apparatus shown in'-;Figures'1 and 2, wherein translation efiiciency is normally low or, as shown, zero and begins to rise coincidentally with oscillations produced inthe apparatus shown in Figures 3 and 4, wherein translation efii 'ciency is normally high but is reduced to a before excitation. Curve N may represent oscillations produced in the apparatus shown in;

. Figure 5, wherein translation efiiciency isto rise at a definite time after excitation,

normally low or, as shown, zero and begins for example, to the employment of tube fi1a ments of high thermal inertia. It will be understood that these curves are illustrative only, and are susceptible of modification in form, steepness, etc., as the result of choice and arrangement of circuit components.

Wide further modifications in and substitutions for the apparatus shown in the figures may'of course be made without de parture in manner of employment from the novel general method of varying translation efficiency about andafter the instant of orig inal excitation of the tuned body thus, for example, key-actuated mechanical devices,

or ele'ctro-thermalmechanical systems e1ec-- -ctrically operated by the keys, may be employed to move the translating devices with respect to the vibrating bodies. It will also be appreciated that the general arrangements hereinabove disclosed are not limited in usefulness to the capacitive mechanico-electric translating devices illustrated, being available for use with other translating devices, I

as for example to delay the rise of magnetizing current in an electromagnetic translating device. It will finally be seen that we have disclosed, among other things, an instrument employing for excitation of its tuned bodies the simple and flexible method of percussion, together with means and methods for freeing the instrument of the limitation of producing only a percussion type oftone. f

We claim:

1. In a musical instrument of the type wherein tuned bodies are selectively vibrated and their vibrations translated into electric oscillations and thence into sound, the method of variously establishing the tone commencement characteristics, which consists in provoking a variation of the efiiciency of such translation of vibration of each body coincidentally to the starting of such vibration, and in selectively adjusting the rate of such variation. l 2. In a musical instrument, the combinationof a pluralityof tuned-bodies; indiv -idual means associated with each of said bodies .for exciting it into vibration; atleast one mechanico-electric system'for translating into electric oscillations the vibrations of said bodies; means connected to and coacting with each of said first-mentioned means, for varying the efiiciency of such translation of vibration of the associated said body; and selective means for adj 'nsting therate of such efliciency variation.

. 3; In a muslcal controlled by a key for vibrating each of sald bodies; mechanico-electric apparatus for translating into electric oscillations the vlbrations of said bodies and an individual electric circuit associated with each body for regulating the efiiciency of such translation of the vibration of said body, each said circuit including a variable element connected with the corresponding said key, said element being variable in accordance with pressure on said; key.

4. In a musical instrument, the combination of a plurality of tuned bodies; means instrument, the combination of a plurality of tuned bodies; means controlled by a key for vibrating each of said 7 ductive bodies; a devic'e actuated by a key for,

'of fixed D. C. potential;

exciting each of said bodies into vibration;

at least one electrically conductive member,

ages across said resistances, said means ineluding a source of D. C. potential containing the potential of said P011113, an individual system of series resistances for each of said bodies shunting said source, and a connection from each of said bodies to a point in its associated said resistance system; and individual automatic means for varying the efliciency of said first-mentioned means in a definite manner, said automatic means including a variable element in each said resistance system, operatively connected to the associated said key, and at least oneelectrical capacity associated with each said resistance system.

6. In a musical instrument, the combination of a plurality of tuned, electrically conductive bodies; a device actuated by a key for exciting each of said bodies into vibration; at least one'electrically conductive member, each said member forming an electrical capacity with a vibratable ortion of each of said bodies; a resistance rom each of said electrically conductive members to a point means for causing sa1d vlbratlons of said bodies to produce voltages across said resistances, said means including a source of D. lty of two-element vacuum tubes, the anode C. potential, a pluralof each such t'ube being connected to a difl'erent one of said bodies, a source of filament current for all of said tubes, 9. connection from said filament source to the negative terminal of said D. C. potential source, and a resistance from each of said bodies, to said point of fixed potential; and individual automatic means for varying the efiiciency of said first-mentioned means in a definite manner, said automatic means including a device for controlling the filament current of each said tube, operatively connected to the associated said ey W Y 7. In a musical instrument, the combination of a plurality of tuned bodies; a device actuated b a normally raised key for exciting each 0 said bodies into vibration; a ile of thin discs of resistance material un erling the vibration thereof; means for trans-- latmg electric oscillations-from said vibration; means operative in a predetermined time relationship to the-operation of said controlling means for varymg the efliciency of said translating means; and selective means for adjusting the rate of such variation.

BENJAMIN F. MIESSNER. CHARLES T. JACOBS. 

